Transparent fiber channel concentrator for point to point technologies

ABSTRACT

A data processing system for transferring data from a first plurality of data links to a second plurality of data links is provided. A data bridge is initialized. The data bridge is functionally connected on a first end to the first plurality of data links and on a second end to the second plurality of data links. A determination is made if a first data link within the first plurality of data links and a second data link within the second plurality of data links initiate a login parameter. Data is automatically transferred from a source data link within the first plurality of data links to a target data link within the second plurality of data links based on the login parameter.

TECHNICAL FIELD

The present invention is directed to a path balancing apparatus andmethod. In particular, the present invention is directed to an apparatusand method for multiplexing along multiple communication paths to aplurality of devices. Still more particularly, the present invention isdirected to an apparatus and method for multiplexing along multiplecommunication paths to a plurality of devices without an externalswitching device.

DESCRIPTION OF RELATED ART

With the relatively high costs of a Fibre Channel data path, it isimportant to use as much of the available path bandwidth as possible.Currently, in many user environments, the data path may be underutilizedwith a single Fibre Channel (FC) port. One way to mitigate the costs ofthe data path is to provide connectivity for more than a single FC portso that the power of the data path may be fully utilized. If data pathsare shared by FC ports with small incremental cost additions and nosignificant reduction in performance, the user may see greaterhost/device connectivity at a lower cost per port. Therefore, it wouldbe advantageous to have an apparatus and method for sharing a data pathbetween multiple FC ports.

SUMMARY OF THE INVENTION

The present invention provides a data processing system for transferringdata from a first plurality of host data links to at least a singlelocal data link. A data bridge is initialized. The data bridge isfunctionally connected on a first end to the first plurality of datalinks and on a second end to the second plurality of data links. Adetermination is made if a first data link within the first plurality ofdata links and a second data link within the second plurality of datalinks initiate a login parameter. Data is automatically transferred froma source data link within the first plurality of data links to a targetdata link within the second plurality of data links based on the loginparameter.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the invention are setforth in the appended claims. The invention itself, however, as well asa preferred mode of use, further objectives and advantages thereof, willbest be understood by reference to the following detailed description ofan illustrative embodiment when read in conjunction with theaccompanying drawings, wherein:

FIG. 1 is an exemplary block diagram of connectivity for more than asingle FC port in accordance with a preferred embodiment of the presentinvention;

FIG. 2 is an exemplary block diagram of a single port PCI mezzanine FCboard is illustrated in accordance with a preferred embodiment of thepresent invention;

FIG. 3 is an exemplary block diagram of a class 3 login frame exchangebetween a host and the local FC port utilizing a fibre channelconcentrator PCI mezzanine board in accordance with a preferredembodiment of the present invention;

FIG. 4 is an exemplary high level block diagram of a fibre channelconcentrator integrated circuit hardware in accordance with a preferredembodiment of the present invention;

FIG. 5 is an exemplary flow diagram describing the states of fibrechannel concentrator main state machine during the link initializationprocess in accordance with a preferred embodiment of the presentinvention;

FIGS. 6A and 6B are exemplary flow diagrams describing the logininitialization during a main active state in accordance with a preferredembodiment of the present invention; and

FIG. 7 is an exemplary flow diagram describing the reception of a fabriclogin frame when the fibre channel concentrator is not in the loginlockout state in accordance with a preferred embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention provides an apparatus and method by which todirectly connect a plurality of hosts to a single fibre channel (FC)link without the need of an external switch. This provides connectivitybenefits in which the hosts are using only a portion of the linkbandwidth. Hardware may be used to allow the hosts to transparentlyshare the FC link into an FC controller. This hardware may acts as a FCframe multiplexer/demultiplexer with buffering capability. Receiveframes from the plurality of external ports are multiplexed onto thelocal FC link. Transmit frames on the local FC link are routed by adestination identifier (ID) to one of the external ports.

FIG. 1 is an exemplary block diagram of connectivity for more than asingle FC port in accordance with a preferred embodiment of the presentinvention. A solution to mitigation of the costs of the data path is toprovide connectivity for more than a single FC port so that the power ofthe data path may be fully utilized. If data paths are shared by FCports with small incremental costs additions and no significantreduction in performance, a greater host/device connectivity may beprovided which results in a lower cost per FC port. Therefore, in thisexample, concentrator 100 merges FC point to point physical links 102into a single FC link 104 by the processes of the present invention.

FIG. 2 is an exemplary block diagram of a single port PCI mezzanine FCboard is illustrated in accordance with a preferred embodiment of thepresent invention. FIG. 2 provides further detail of FIG. 1.Concentrator device 202 may have several improved characteristics overthe prior art. For example, concentrator device 202 may be transparentto external FC hosts/devices, require little or no management, data needonly flow between the host port(s) and the local FC port and may supportclass 2 and class 3 frame exchanges. Concentrator 202 acts as a physicallayer end-point and provides a bridging function to move frames betweenexternal links and local links.

In this example, concentrator 202 may consist of a local FC port 204 anda plurality of host ports 206. One local port is shown in this examplebut any number of local ports may be employed in accordance with apreferred embodiment of the present invention. In addition, three hostports are shown in this example but any number of host ports may beemployed in accordance with a preferred embodiment of the presentinvention. Furthermore, concentrator 202 may also consist of bufferdirect memory access (DMA) controller 208.

Concentrator 202 may achieve a variety of states during the first stageof an initialization process, such as, for example,

-   -   a. main_reset: the main_reset state may be entered at power-up        or if both the local link and all of the external links have        gone to an offline state. In the main-reset state, all of the        links may be forced offline. Concentrator 202 then monitors an        incoming signal from the links and if a local link and one or        more of the external links have received a valid FC primitive        sequence, the internal state of concentrator 202 advances to a        main-online state.    -   b. main_online: the main_online state turns on all of the local        links and external links if the links have received a valid        primitive sequence and allowed to progress through a FC link        state initialization protocol until the link is in an active        state.    -   c. main_active: the main_active state is the normal active        operating state. In the main_active state frame traffic may        occur.    -   d. main_offline: the main_offline state occurs in concentrator        202 if a local link or all of the external links drop out of the        main_active state at any time. While in the main_offline state,        all of the active links are forced offline. When each link        completes the offline protocol, concentrator 202 returns to the        main-reset state in order to re-initialize the links.        The achievement of the variety of states during the first stage        of an initialization process is further illustrated in FIG. 5.

After the main_active state is achieved, FC end-points (hosts and locallinks) initiate fabric login and port login in order to pass operatingparameters. The initiation of fabric login and port login is importantto concentrator 202 because buffer credits and port identification areestablished during the fabric and port logins. Special states areentered when fabric and port login frames are detected. An example ofthese special states is:

-   -   main-flogi (fabric login): Concentrator 202 enters this special        state when a fabric login frame is received from an external        link. While in this state, and main_plogi described below, only        frames received from the same link as the fabric login are        forwarded to the local link. Frames received from other external        links are held in buffers, such as, for example, buffer RAM 210        until the login lockout is complete. Any login type frames, for        example, flogi, plogi or acc (login acknowledge) received from        the local link are forwarded to the initiating fabric login        external link. Any other frames received from the local link are        forwarded to the appropriate external link as indicated by the        local link's destination identifier.    -   main_plogi (main port login): The main_plogi state is a        continuation of the login process. The main_plogi state is        entered when a port login frame is received from an external        link. When a login acknowledge (acc) is received from the local        link, the login process is complete and concentrator 202 returns        to the main_active state. The destination identifier field of        the acc (N-port parameters) is captured and used to compare with        the destination identifier of subsequent frames to determine        which external link to route outbound frames from the local        link. The process of entering the special states when fabric and        port login frames are detected is further illustrated in FIGS.        6A and 6B.

However, a condition may arise in which a fabric login is received froma local link and concentrator 202 is not in a login lockout state. Thisscenario is possible if the local link is the first to attempt a fabriclogin after initialization. If the destination identifier from the locallink is a valid match for one of the external links, the frame isforwarded to the associated external link. Otherwise, if the destinationidentifier is not a valid match for one of the external links, the framemay be held in buffer RAM 210 by concentrator 202 until the loginlockout states are properly entered due to a login initiated by anexternal state, at which point the frame is forwarded to the externallink. This process is further explained in FIG. 7.

Data is routed through concentrator 202. In particular, concentrator 202receives data from a variety of sources, which may be from, for example,a local link consisting of FC transceiver 216 and optical transceiver218 or from a plurality of external links. In this example, opticaltransceivers 220, 222 and 224 in conjunction with quad FC transceiver214 comprise the external links. The process of bringing external FClinks and the local FC link from a power-up or reset state to receivingactive data traffic may involve two main milestones. First, the locallinks and at least one external link may be brought to the active state.Then the local links and the external link ports complete the fabriclogin protocols and the port login protocols, which define the portidentification (ID) and allow concentrator 202 hardware to direct framesto the proper external FC link destination.

Reference oscillator 212 provides a clock signal for the input andoutput of the data. Data received by concentrator 202 may send the datadirectly from local port 204 to host port(s) 206 through buffer DMAcontroller 208 or may store the data in buffer ram 210 via data link236. In addition, control signal 232 and address signal 234 flows frombuffer DMA controller 208 and buffer RAM 210. The present invention, asillustrated in FIG. 2, is not confined to providing data in only onedirection. In other words, quad transceiver 214 may either output datato concentrator 202 or input data from concentrator 202. Likewise, FCtransceiver 216 may either output data to concentrator 202 or input datafrom concentrator 202.

The operation of concentrator 202 is as follows. Optical transceivers,such as for example, optical transceivers 220, 222 and 224 may provideinput into quad FC transceiver 214. Furthermore, quad FC transceiver 214may accept input from reference oscillator (OSC) 212. Quad FCtransceiver 214 takes the input from optical transceivers 220, 222 and224 as well as the input from reference OSC 212 and in turn providesinput into concentrator 202 via host port(s) 206. In turn, host port(s)206 send the inputted data to buffer DMA controller 208. Buffer DMAcontroller 208 receives the data and sends the data to buffer RAM 210for temporary storage. All received data passes through buffer RAM 210.Buffer RAM 210 is used to store data frames received on the links. Datais held in buffer RAM 210 until the frame is transmitted by one of theFC links. Although buffer RAM 210 supports bi-directional data, thisimplementation uses one of the data busses to write data and the otherfor read data so the data movement is unidirectional.

Data comes from host port 206 via both buffer DMA controller 208 as wellas buffer RAM 210, and is then sent to local port 204. In oneembodiment, local port 204 receives data from and transmits data to FCtransceiver 216, which in turn transmits the data to optical transceiver218. In another embodiment, local port 204 transmits data to andreceives data from local FC controller 226, which in turn transmits datato and receives data from PCI bus interface 229. Local FC controller 226receives control input 228 and address/data input 230 through PCI businterface 229 and provides control input 228 to concentrator 202.

FIG. 3 is an exemplary block diagram of a class 3login frame exchangebetween a host and local port utilizing a fibre channel concentrator PCImezzanine board in accordance with a preferred embodiment of the presentinvention. FIG. 3 illustrates class 3 login frame exchanges between hostport 302 and local port 306 with concentrator 304 between host port 302and local port 306.

In this example, main_active state transitions are illustrated.Concentrator 304 consists of external link port (EL) 308 and local linkport (LL) 310. Link endpoint concentrator 304 is involved in buffer tobuffer flow control across external link 308 and local link 310.However, concentrator 304 may not be involved in end to end flowcontrol, therefore, acc frames may be forwarded in a similar manner asany other frame. Concentrator 304 monitors for login frames such aslogin frames 312 and 324 and captures remote buffer to buffer creditparameters for each link as the link is logged in. When the link isreset, the remote credit for each link is set to a value of 1. SeparateBuffer-to-Buffer (BB) credit counters are maintained for each link andframes and are transmitted only if the BB credit count is less than theremote buffer to buffer credit parameter.

FIG. 4 is an exemplary high level block diagram of a fibre channelconcentrator integrated circuit hardware in accordance with a preferredembodiment of the present invention. In this example, within the fibrechannel concentrator 202 in FIG. 2 are four independent FC link datapaths 432 a/434 a, 432 b/434 b, 432 c/434 c and 432 d/434 d withindependent link state machines 422 a, 422 b, 422 c and 422 d,respectively. Link state machines 422 a, 422 b, 422 c and 422 d mayprovide output to buffer memory control block 420. In addition, thereare separate blocks for main state machine 402, buffermanagement/forwarder 426, frame cracking header 404 and controlinterface 406.

In this example, FC link interface blocks 401 a, 401 b, 401 c and 401 dwithin concentrator 202 in FIG. 2 may be identical. Each link interface401 a, 401 b, 401 c and 401 d may be divided into, for example, threemain functions. For example, receive data path 434 a, transmit data path432 a and link state machine 422 a comprise link interface 401 a. Datapaths 432 a and 434 a may be independent and unidirectional. Flowcontrol information may be passed between the data paths. Link statemachine 422 a may be used to execute link initialization and errorrecovery protocols.

Link state machines 422 a, 422 b, 422 c and 422 d execute the linkinitialization and error recovery protocols. Link state machines 422 a,422 b, 422 c and 422 d monitor the primitive sequences detected by areceive data path, for example receive data path 434 a, to generateordered sets based on the current link state. Frame buffer SRAMcontroller 420 controls access to an external frame buffer synchronousSRAM via write data path 412, address path 414 and read data path 416.Frame buffer SRAM controller 420 accepts separate buffer address fromtransmit and receive data paths from FC links 401 a, 401 b, 401 c and401 d, as well as write data from each receive data path. Each data pathmay be guaranteed one-fourth of the total access bandwidth. Anacknowledge message is passed to each data path to enable dataread/write from a FIFO's and address increment.

Buffer management/forwarder 426 maintains the buffer queues for each ofthe FC links. Buffer management/forwarder 426 communicates to transmitdata paths 432 a, 432 b, 432 c and 432 d as to where the transmit datapaths' next transmit buffer is located and communicates to receive datapaths 434 a, 434 b, 434 c and 434 d where to store incoming frames.Buffer management/forwarder 426 directs the forwarding of receivedframes to the proper transmitter based on the input from frame headercrack 404.

Frame header crack 404 examines the contents of each frame transmittedand received from a local port. Frame header crack 404 specificallychecks for FLOGI and PLOGI frames and the corresponding ACK frames whichmay be used for special login sequences. Frame header crack 404 extractsBB credit parameters from the frames during initialization and passesthe BB credit parameters to the individual FC link controllers. Frameheader crack 404 also captures during login the destination ID of theexternal link so that when normal frames are received from the locallink the identifier can be compared and the frame forwarded to theproper destination.

Main state machine 402 coordinates the initialization of concentrator202 as a whole, including reset, online/offline enabling, and speciallogin sequences. Main state machine 402 monitors the individual linkstates and receives input from frame header crack 404. Control interface406 supports external I2C interface 408 protocol allowing access tointernal registers and status.

FIG. 5 is an exemplary flow diagram describing the states of fibrechannel concentrator main state machine during the link initializationprocess in accordance with a preferred embodiment of the presentinvention. In this example, the operation starts with powering up thesystem (step 502). The main_reset state is entered (step 504) and then adetermination is made as to whether or not both local links and externallinks are offline (step 506). If both local links and external links arein the offline state (step 506:YES), the links are forced offline (step508) and the operation returns to step 504 where the main_reset state isentered. If both the local link and the external links are not in theoffline state (step 506:NO), the incoming signal is monitored (step510). Then a determination is made as to whether or not the local linksand one or more external links are alive (step 512). If the local linkand one or more external links are not alive (step 512:NO), theoperation returns to step 510 where the incoming signal is monitored.

If the local link and one or more external links are alive (step512:YES), the operation advances to the main_online state (step 514).The links are turned online (step 516) and then the link stateinitialization protocol is activated (step 518). The progression throughlink state initialization protocol is allowed to proceed (step 5206).Then a determination is made as to whether or not the system is in themain_active state (step 522). If the system is not in the main_activestate (step 522:NO), the operation returns to step 520 where theprogression through the link state initialization protocol is allowed.If the system is in the main_active state (step 522:YES), the systemallows frame traffic to flow (step 524). Then a determination is made asto whether the local link or all of the external links are not active(step 526).

If the local link and one or more of the external links are active (step526:NO), the operation returns to step 524 where the frame traffic isallowed to flow. If the local link or all of the external links are notactive (step 526:YES), the main_offline state is entered (step 528). Thelinks are forced offline (step 530) and then a determination is made asto whether or not the links have completed offline protocol (step 532).If the links have not completed offline protocol (step 532:NO), theoperation returns to step 530 where the links are forced offline. If thelinks have completed offline protocol (step 532:YES), the operationreturns to step 504 where the main_reset state is entered.

FIGS. 6A and 6B are exemplary flow diagrams describing the logininitialization during a main active state in accordance with a preferredembodiment of the present invention. In this example, the operationbegins with a determination as to whether or not the main_active statehas been achieved (step 602). If the main_active state has not beenachieved (step 602:NO), the operation performs in accordance with anyother achieved states (step 642). If the main_active state has beenachieved (step 602:YES), fabric login is initiated (step 604). Then portlogin is initiated (step 606). Then a determination is made as towhether or not fabric login and port login frames are detected (step608). If fabric login and port login frames are not detected (step608:NO), the operation continues to determine as to whether or notfabric login and port login frames have been detected (step 608). Iffabric login and port login frames have been detected (step 608:YES), adetermination is made as to whether or not a fabric login frame has beenreceived from an external link (step 610). If a fabric login frame hasnot been received from an external link (step 610:NO), the operationreturns to step 608 where a determination is made as to whether or notfabric login and port login frames have been detected.

If a fabric login frame has been received from an external link (step610:YES), the main_flogi state is entered (step 612). Then adetermination is made as to whether or not a frame has been receivedfrom the same link as the fabric login (step 614). If a frame has notbeen received from the same link as the fabric login (step 614:NO), theframe is held in a buffer (step 616). Then a determination is made as towhether or not a login lockout is complete (step 620). If the loginlockout is not complete (step 620:NO), the operation returns to step 616where the frame is held in a buffer. If the login lockout is complete(step 620:YES), the frame is forwarded to the local link (step 618).

Returning to step 614, if the frame is received from the same link asthe fabric login (step 614:YES), the frame is forwarded to the locallink (step 618). The frames from the local link are received (step 622)and then a determination is made as to whether or not the frames are tobe forwarded to the initiating fabric login external link (step 626). Ifthe frames are not to be forwarded to the initiating fabric loginexternal link (step 626:NO), the frames received from the local linksare forwarded to the appropriate external link as indicated by thedestination identifier (step 630) and thereafter the operationterminates. If the frames are to be forwarded to the initiating fabriclogin external link (step 626:YES), then the frames are forwarded to theinitiating fabric login external link (step 628) and thereafter theoperation terminates.

Returning to step 608, if the fabric login and port login frames are notdetected (step 608:NO), a determination is made as to whether or not theport login frame has been received from the external link (step 632). Ifthe port login frame has not been received from the external link (step632:NO), the operation returns to step 608 in which to determine as towhether or not the fabric and port login frames have been detected. Ifthe port login frame has been received from the external link (step632:YES), the main_plogi state is entered (step 634). Then adetermination is made as to whether or not the login acknowledge (Acc)has been received from the local link (step 636). If the “Acc” has notbeen received from the local link (step 636:NO), the operation returnsto step 632 where a determination is made as to whether or not the portlogin frame has been received from the external link. If the “Acc” hasbeen received from the local link (step 636:YES), the destination fieldis captured from the login acknowledge (acc) (step 638). The destinationidentifier is then compared with the destination field of subsequentframes to determine which external link to route outbound frames fromthe local link (step 640) and thereafter the operation returns to step604 where the fabric login is initiated.

FIG. 7 is an exemplary flow diagram describing the reception of a fabriclogin frame when the fibre channel concentrator is not in the loginlockout state in accordance with a preferred embodiment of the presentinvention. In this example, the operation starts with a determination asto whether or not a frame is received from a local link (step 702). If aframe is not received from a local link (step 702:NO), the operationterminates. If a frame is received from a local link (step 702:YES), adetermination is made as to whether or not the system is in the loginlockout stage (step 704). If the system is not in the login lockoutstage (step 704:NO), the frame is stored and the operation returns tostep 704 to determine whether or not the system is in the login lockoutstage. If the system is in the login lockout stage (step 704:YES), adetermination is made as to whether or not the destination identifier ofthe local link matches the destination identifier of the external link(step 706).

If the destination identifier of the local link does not match thedestination identifier of the external link (step 706:NO), the frame isstored (step 710) and the operation returns to step 704 to determinewhether the system is in login lockout stage. If the destinationidentifier of the local link does match the destination identifier ofthe external link (step 706:YES), the frame is forwarded to theassociated external link (step 708) and thereafter the operationterminates.

Therefore, the present invention provides the ability to connect aplurality of hosts to a single fibre channel link without the need of anexternal switch. This provides connectivity benefits such as, forexample, using as much of the available bandwidth as possible,mitigating the costs of the data path and no reduction in performance inwhich the user may see greater host/device connectivity at a lower costper port.

The description of the present invention has been presented for purposesof illustration and description, but is not intended to be exhaustive orlimited to the invention in the form disclosed. Many modifications andvariations will be apparent to those of ordinary skill in the art. Theembodiment was chosen and described in order to best explain theprinciples of the invention, the practical application, and to enableothers of ordinary skill in the art to understand the invention forvarious embodiments with various modifications as are suited to theparticular use contemplated.

1. A method in a data processing system for transferring data from aplurality of host data links to at least one local data link, the methodcomprising the steps of: initializing a data bridge, wherein the databridge is functionally connected on a first end to the plurality of hostdata links and on a second end to the at least one local data link, andwherein all connections to the data bridge are made through fibrechannel ports; operating the data bridge to capture credit parameters,for use in determining if a first data link within the plurality of hostdata links and a second data link within the at least one local datalink initiate a login parameter; and automatically transferring the datafrom a source data link within the plurality of host data links to atarget data link within the at least one local data link based on thelogin parameter, wherein the data transferred from the source data linkis stored in a memory buffer device, and wherein the memory bufferdevice is connected to the data bridge.
 2. The method of claim 1,wherein the memory buffer device is connected to the data bridge via amemory buffer controller, and the memory buffer device and the memorybuffer controller are both connected to the source data link through aninput port of the data bridge, and are also both connected between thesource data link and the target data link.
 3. The method of claim 1,wherein the data bridge is a data link concentrator.
 4. The method ofclaim 1, wherein initializing the data bridge includes resetting thedata bridge.
 5. The method of claim 4, wherein if the data bridge isreset, the plurality of host data links functionally connected to thedata bridge and the at least one local data link functionally connectedto the data bridge are forced offline by the data bridge.
 6. The methodof claim 4, further comprising: monitoring a signal from the first datalink within the plurality of host data links and a signal from thesecond data link within the at least one local data link functionallyconnected to the data bridge; determining whether an initiating sequencesignal is received by the first data link and the second data link; andestablishing a data bridge active state if the initiating sequencesignal is received by the first data link and the second data link. 7.The method of claim 6, further comprising: terminating data transferfrom the source data link within the plurality of host data links to thetarget data link within the at least one local data link if the databridge is in an offline state.
 8. The method of claim 6, furthercomprising: monitoring the plurality of host data links and the at leastone local data link functionally connected to the data bridge; andterminating data transfer from the source data link to the target datalink if the plurality of host data links or the at least one local datalink does not remain in an active state.
 9. The method of claim 8,wherein if the plurality of host data links and the at least one localdata link complete an offline state protocol, the data bridge is reset.10. The method of claim 1, wherein the login parameter includes a fibrechannel fabric login parameter and a fibre channel part login parameter.11. The method of claim 10, wherein the fibre channel login parameterincludes buffer credits.
 12. The method of claim 10, wherein the fibrechannel port parameter includes a port identification.
 13. The method ofclaim 1, further comprising: automatically transferring the data from asource data link within the plurality of host data links to a bufferdevice if the data bridge is in a lockout mode.
 14. An apparatus fortransferring data from a plurality of host data links to at least onelocal data link, comprising: and array of data links; and a data bridgecoupled on a first end to the plurality of host data links and onesecond end to the at least one local data link, wherein the data bridgeis initialized, wherein all connections to the data bridge are madethrough fibre channel ports, the data bridge determines if a first datalink within the plurality of host data links ad a second data linkwithin the at least one local data link initiate a login parameter, andthe data bridge automatically transfers the data from a source data linkwithin the plurality of host data links to a target data link within theat least one local data link based on the login parameter, wherein thedata transferred from the source link is stored in a memory bufferdevice, and wherein the memory buffer device is connected to the databridge.
 15. The apparatus of claim 14, wherein the memory buffer deviceis connected to the data bridge via a memory buffer controller, and thememory buffer device and the memory buffer controller are both connectedto the source data link through an input port of the data bridge, andare also both connected between the source data link and the target datalink.
 16. The apparatus of claim 14, wherein the data bridge is a datalink concentrator.
 17. The apparatus of claim 14, wherein initializingthe data bridge includes resetting the data bridge.
 18. The apparatus ofclaim 17, wherein if the data bridge is reset, the plurality of hostdata links functionally connected to the data bridge and the at lest onelocal data link functionally connected to the data bridge are forcedoffline by the data bridge.
 19. The apparatus of claim 17, wherein ifthe data bridge monitors a signal from the first data link and a signalfrom the second data link functionally connected to the data bridge, thedata bridge determines whether an initiating sequence signal is receivedby the first data link and the second data link, a data bridge activestate is established if the initiating sequence signal is received bythe first data link and the second data link.
 20. The apparatus of claim19, wherein the data bridge terminates data transfer from the sourcedata link to the target data link if the data bridge is in an offlinestate.
 21. The apparatus of claim 19, wherein the data bridge monitorsthe plurality of host data links and the at least one local data linkfunctionally connected to the data bridge and the data bridge terminatesdata transfer from the source data link to the target data link if theplurality of host data links or the at least one local data link doesnot remain in an active state.
 22. The apparatus of claim 21, wherein ifthe plurality of host data links and the at least one local data linkcomplete an offline state protocol, the data bridge is reset.
 23. Theapparatus of claim 14, wherein the login parameter includes a fibrechannel fabric login parameter and a fibre channel port login parameter.24. The apparatus of claim 23, wherein the fibre channel login parameterincludes buffer credits.
 25. The apparatus of claim 23, wherein thefibre channel port parameter includes a port identification.
 26. Theapparatus of claim 14, wherein the data bridge automatically transfersthe data from a source data link to a buffer device if the data bridgeis in a lockout mode.